What Scares Bug Experts?:The horrible disease that experts feared would come to the United States has come to the United States.

If your wife is a researcher in medical entomology, you’ll often hear odd tidbits related to mosquito-borne diseases. For instance, did you know how cute malaria parasites can look under a microscope? I didn’t either, until I met Cassandra Urquhart. (Some other things I’ve heard described as “cute” since then include, but are not limited to: cockroaches, nematodes, spiders, earwigs, and male mosquitoes.) She’s fascinated by her own work with La Crosse virus, excited by new papers on dengue fever, and interested in how many of the mosquitoes she’s collected at sites around Knox County, Tennessee will test positive for West Nile virus. In her spare time, she reads books on the history of yellow fever and Chagas disease for fun. Don’t get me wrong—she cares about the human toll of such diseases. But as a scientist, she’s usually more curious than alarmed about them. However, when it comes to chikungunya virus, my cheerfully bug-obsessed wife gets far more serious—and so do many entomologists. So why is chikungunya different?

Chikungunya virus seems, at first, to have a lot in common with dengue virus, another mosquito-borne pathogen. Both cause extremely painful diseases—chikungunya’s name comes from a Makonde word meaning “that which bends up,” referring to the contortions sufferers put themselves through due to intense joint pain. Dengue’s nickname is breakbone fever. Both viruses are primarily transmitted by the Aedes aegypti mosquito, and both have been moving slowly closer to the United States over the past decades, with local cases of dengue fever already found in Florida and Texas.

Last week the Centers for Disease Control and Prevention announced the first locally acquired cases of chikungunya in the United States. A woman in Miami-Dade County and a man in Palm Beach County, neither of whom had left the country recently, both came down with the dreaded disease.

Chikungunya doesn’t need a reservoir—it can be spread directly from one human host to another.